RESUMO
Women older than 60 have a higher risk of dementia, aging-related cognitive decline, and Alzheimer's Disease (AD) than the rest of the population. The main reason is hormonal senescence after menopause, a period characterized by a decline in estrogen levels. Since the effectiveness of drugs currently approved for the treatment of AD is limited, it is necessary to seek the development of new therapeutic strategies. Vitamin D deficiency is prevalent in AD patients and individuals with dementia in general. The supplementation of this vitamin in dementia patients might be an interesting approach for increasing the effectiveness of pre-existing medications for dementia treatment. Thus, the present study aims to investigate the effect of vitamin D treatment associated with memantine and donepezil in female mice submitted to ovariectomy (OVX) for five months and subjected to a dementia animal model induced by intracerebroventricular injection of aggregated amyloid ßeta (Aß1-42). For this purpose, Balb/c mice were divided into five experimental groups, which received 17 days of combined therapy with vitamin D, donepezil, and memantine. Then, animals were subjected to behavioral tests. OVX groups exhibited reduced levels of estradiol (E2) in serum, which was not altered by the combined therapy. Higher levels of vitamin D3 were found in the OVX animals submitted to the triple-association treatment. Mice exposed to both OVX and the dementia animal model presented impairment in short and long-term spatial and habituation memories. Also, female mice exposed to Aß and OVX exhibited a reduction in brain-derived neurotrophic factor (BDNF) and interleukin-4 (IL-4) levels, and an increase in tumor necrose factor-α (TNFα) levels in the hippocampus. Besides, increased levels of IL-1ß in the hippocampus and cerebral cortex were observed, as well as a significant increase in immunoreactivity for glial fibrillary acidic protein (GFAP), an astrocytes marker, in the hippocampus. Notably, triple-association treatment reversed the effects of the exposition of mice to Aß and OVX in the long-term spatial and habituation memories impairment, as well as reversed changes in TNFα, IL-1ß, IL-4, and GFAP immunoreactivity levels in the hippocampus of treated animals. Our results indicate that the therapeutic association of vitamin D, memantine, and donepezil has beneficial effects on memory performance and attenuated the neuroinflammatory response in female mice subjected to OVX associated with a dementia animal model.
Assuntos
Doença de Alzheimer , Fármacos Neuroprotetores , Camundongos , Feminino , Animais , Memantina/farmacologia , Memantina/uso terapêutico , Donepezila/metabolismo , Donepezila/farmacologia , Fármacos Neuroprotetores/farmacologia , Fármacos Neuroprotetores/uso terapêutico , Vitamina D/farmacologia , Interleucina-4/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/metabolismo , Vitaminas , Hipocampo/metabolismo , Peptídeos beta-Amiloides/metabolismoRESUMO
Biological membranes show lateral and transverse asymmetric lipid distribution. Cholesterol (Chol) localizes in both hemilayers, but in the external one it is mostly condensed in lipid-ordered microdomains (raft domains), together with saturated phosphatidyl lipids and sphingolipids (including sphingomyelin and glycosphingolipids). Membrane asymmetries induce special membrane biophysical properties and behave as signals for several physiological and/or pathological processes. Alzheimer's disease (AD) is associated with a perturbation in different membrane properties. Amyloid-ß (Aß) plaques and neurofibrillary tangles of tau protein together with neuroinflammation and neurodegeneration are the most characteristic cellular changes observed in this disease. The extracellular presence of Aß peptides forming senile plaques, together with soluble oligomeric species of Aß, are considered the major cause of the synaptic dysfunction of AD. The association between Aß peptide and membrane lipids has been extensively studied. It has been postulated that Chol content and Chol distribution condition Aß production and posterior accumulation in membranes and, hence, cell dysfunction. Several lines of evidence suggest that Aß partitions in the cell membrane accumulate mostly in raft domains, the site where the cleavage of the precursor AßPP by ß- and γ- secretase is also thought to occur. The main consequence of the pathogenesis of AD is the disruption of the cholinergic pathways in the cerebral cortex and in the basal forebrain. In parallel, the nicotinic acetylcholine receptor has been extensively linked to membrane properties. Since its transmembrane domain exhibits extensive contacts with the surrounding lipids, the acetylcholine receptor function is conditioned by its lipid microenvironment. The nicotinic acetylcholine receptor is present in high-density clusters in the cell membrane where it localizes mainly in lipid-ordered domains. Perturbations of sphingomyelin or cholesterol composition alter acetylcholine receptor location. Therefore, Aß processing, Aß partitioning, and acetylcholine receptor location and function can be manipulated by changes in membrane lipid biophysics. Understanding these mechanisms should provide insights into new therapeutic strategies for prevention and/or treatment of AD. Here, we discuss the implications of lipid-protein interactions at the cell membrane level in AD.
RESUMO
Alzheimer's disease (AD) is a complex neurodegenerative disorder associated with the aggregation of the amyloid-beta peptide (Aß) into large oligomers and fibrils that damage healthy brain cells. The predominant peptide fragments in the plaques are mainly formed by the Aß1-40 and Aß1-42 peptides, albeit the eleven-residue Aß25-35 segment is largely used in biological studies because it retains the neurotoxic properties of the longer Aß peptides. Recent studies indicate that treatment with therapeutic steroid hormones reduces the progress of the disease in AD models. Particularly, treatment with 17ß-aminoestrogens (AEs) has shown a significant alleviation of the AD development by inhibiting oxidative stress and neuronal death. Yet, the mechanism by which the AE molecules exhibit their beneficial effects remains speculative. To shed light into the molecular mechanism of inhibition of the AD development by AEs, we investigated the possibility of direct interaction with the Aß25-35 peptide. First, we calculate various interacting electronic properties of three AE derivatives as follows: prolame, butolame, and pentolame by performing DFT calculations. To account for the polymorphic nature of the Aß aggregates, we considered four different Aß25-35 systems extracted from AD relevant fibril structures. From the calculation of different electron density properties, specific interacting loci were identified that guided the construction and optimization of various complexes. Interestingly, the results suggest a similar inhibitory mechanism based on the direct interaction between the AEs and the M35 residue that seems to be general and independent of the polymorphic properties of the Aß aggregates. Our analysis of the complex formation provides a structural framework for understanding the AE therapeutic properties in the molecular inhibitory mechanism of Aß aggregation.
Assuntos
Peptídeos beta-Amiloides/química , Estrogênios/farmacologia , Agregados Proteicos , Amino Álcoois/química , Amino Álcoois/farmacologia , Estrenos/química , Estrenos/farmacologia , Estrogênios/química , Modelos Moleculares , Agregados Proteicos/efeitos dos fármacos , Eletricidade EstáticaRESUMO
The main component of Alzheimer's disease (AD) is the amyloid-beta peptide (Aß), the brain of these patients is characterized by deposits in the parenchyma and cerebral blood vessels known as cerebral amyloid angiopathy (CAA). On the other hand, the platelets are the major source of the Aß peptide in circulation and once secreted can activate the platelets and endothelial cells producing the secretion of several inflammatory mediators that finally end up unchaining the CAA and later AD. In the present study we demonstrate that cAMP/PKA pathway plays key roles in the regulation of calpain activation and secretion of Aß in human platelets. We confirmed that inhibition of platelet functionality occurred when platelets were incubated with forskolin (molecule that rapidly increased cAMP levels). In this sense we found that platelets pre-incubated with forskolin (20⯵M) present a complete inhibition of calpain activity and this effect is reversed using an inhibitor of protein kinase A. Consequentially, when platelets were inhibited by forskolin a reduction in the processing of the APP with the consequent decrease in the Aß peptide secretion was observed. Therefore our study provides novel insight in relation to the mechanism of processing and release of the Aß peptide from human platelets.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Plaquetas/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , AMP Cíclico/metabolismo , Adulto , Doença de Alzheimer/sangue , Precursor de Proteína beta-Amiloide/metabolismo , Plaquetas/efeitos dos fármacos , Calpaína/antagonistas & inibidores , Calpaína/metabolismo , Fármacos Cardiovasculares/farmacologia , Células Cultivadas , Colforsina/farmacologia , Simulação por Computador , Humanos , Modelos Moleculares , Selectina-P/metabolismo , Agregação Plaquetária/efeitos dos fármacos , Agregação Plaquetária/fisiologia , Transdução de Sinais/efeitos dos fármacos , Adulto JovemRESUMO
Alzheimer's disease (AD) is the most common cause of dementia worldwide. Despite advances in our understanding of the molecular milieu driving AD pathophysiology, no effective therapy is currently available. Moreover, various clinical trials have continued to fail, suggesting that our approach to AD must be revised. Accordingly, the development and validation of new models are highly desirable. Over the last decade, we have been working with Octodon degus (degu), a Chilean rodent, which spontaneously develops AD-like neuropathology, including increased amyloid-ß (Aß) aggregates, tau hyperphosphorylation, and postsynaptic dysfunction. However, for proper validation of degu as an AD model, the aggregation properties of its Aß peptide must be analyzed. Thus, in this study, we examined the capacity of the degu Aß peptide to aggregate in vitro. Then, we analyzed the age-dependent variation in soluble Aß levels in the hippocampus and cortex of third- to fifth-generation captive-born degu. We also assessed the appearance and spatial distribution of amyloid plaques in O. degus and compared them with the plaques in two AD transgenic mouse models. In agreement with our previous studies, degu Aß was able to aggregate, forming fibrillar species in vitro. Furthermore, amyloid plaques appeared in the anterior brain structures of O. degus at approximately 32 months of age and in the whole brain at 56 months, along with concomitant increases in Aß levels and the Aß42/Aß40 ratio, indicating that O. degus spontaneously develops AD-like pathology earlier than other spontaneous models. Based on these results, we can confirm that O. degus constitutes a valuable model to improve AD research.
Assuntos
Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Amiloide/metabolismo , Encéfalo/patologia , Placa Amiloide/patologia , Doença de Alzheimer/metabolismo , Animais , Encéfalo/metabolismo , Modelos Animais de Doenças , Octodon , Placa Amiloide/metabolismo , Agregados Proteicos , Proteínas tau/metabolismoRESUMO
With the increasing life expectancy of the world's population, neurodegenerative diseases, such as Alzheimer's disease (AD), will become a much more relevant public health issue. This fact, coupled with the lack of efficacy of the available treatments, has been driving research directed to the development of new drugs for this pathology. Metal-protein attenuating compounds (MPACs) constitute a promising class of agents with potential application on the treatment of neurodegenerative diseases, such as AD. Currently, most MPACs are based on 8-hydroxyquinoline. Recently, our research group has described the hybrid aroylhydrazone containing the 8-hydroxyquinoline group INHHQ as a promising MPAC. By studying the known structure-related ligand HPCIH, which does not contain the phenol moiety, as a simplified chemical model for INHHQ, we aimed to clarify the real impact of the aroylhydrazone group for the MPAC activity of a compound with potential anti-Alzheimer's activity. The present work describes a detailed solution and solid-state study of the coordination of HPCIH with Zn2+ ions, as well as its in vitro binding-ability towards this metal in the presence of the Aß(1-40) peptide. Similar to INHHQ, HPCIH is able to efficiently compete with Aß(1-40) for Zn2+ ions, performing as expected for an MPAC. The similarity between the behaviors of both ligands is remarkable. Taken together, the data presented herein point to aroylhydrazones, such as the compounds HPCIH and the previously published INHHQ, as encouraging MPACs for the treatment of AD.
Assuntos
Hidrazonas/química , Nootrópicos/química , Piridinas/química , Zinco/química , Doença de Alzheimer/tratamento farmacológico , Peptídeos beta-Amiloides/metabolismo , Complexos de Coordenação/síntese química , Complexos de Coordenação/química , Complexos de Coordenação/metabolismo , Hidrazonas/síntese química , Hidrazonas/metabolismo , Ligantes , Estrutura Molecular , Nootrópicos/síntese química , Nootrópicos/metabolismo , Fragmentos de Peptídeos/metabolismo , Estudo de Prova de Conceito , Ligação Proteica , Piridinas/síntese química , Piridinas/metabolismo , Zinco/metabolismoRESUMO
Alzheimer's disease (AD) is characterized by amyloid plaques that form due to an increase in amyloid-ß peptide (Aß) aggregation. One strategy in the search of new treatments for AD focuses on compounds that decrease Aß accumulation. Compounds containing a benzofuran ring have been described to play an important role in decreasing Aß-induced toxicity; however, only synthetic benzofurans have been tested thus far. The aim of the present study was to examine the in vitro neuroprotective properties of fomannoxin (Fx), a natural benzofuran isolated from cultures of the Andean-Patagonian fungi Aleurodiscus vitellinus, and evaluate its effect on Aß peptide. We tested the effect of Fx at a wide concentration range (10-11-10-4 M) in PC-12 cells, and found the compound did not alter cellular viability. Fx also showed a concentration-dependent effect on the Aß-induced toxicity in PC12 cells, showing viability above 100% at 10-6 M. We then measured the effect of Fx (10-7-10-5 M) on the frequency of cytosolic Ca2+ transients in rat hippocampal neurons at both acute and chronic (24âh) times. Acute incubation with Fx increased the frequency of cytosolic Ca2+ transients to values around 200%, whereas chronic incubation with Fx increased the frequency of Ca2+ transients. Finally, the Aß-induced decrease in intracellular Ca2+ transients was prevented when Fx (10-6 M) was co-incubated with Aß (5×10-6 M). The results suggest a potent neuroprotective effect of this naturally occurring benzofuran against Aß peptide toxicity that could be mediated by an interference with it binding to plasma membrane, and lead Fx as new chemical entity to develop pharmacological tools against Aß peptide neurotoxicity.
Assuntos
Basidiomycota/química , Benzofuranos/farmacologia , Neurônios/efeitos dos fármacos , Fármacos Neuroprotetores/farmacologia , Placa Amiloide/tratamento farmacológico , Doença de Alzheimer/tratamento farmacológico , Peptídeos beta-Amiloides/toxicidade , Animais , Benzofuranos/química , Benzofuranos/isolamento & purificação , Sobrevivência Celular/efeitos dos fármacos , Hipocampo/patologia , Fármacos Neuroprotetores/química , Fármacos Neuroprotetores/isolamento & purificação , Células PC12 , RatosRESUMO
BACKGROUND: Mild cognitive impairment (MCI) has an increased rate of progression to dementia. Alterations of some metabolic factors, such as deficiency of vitamin D, are a risk factor for cognitive deterioration. Vitamin D is involved in the clearance of ß-amyloid (Aß) from the brain. We have reported that lymphocytes from Alzheimer's disease (AD) patients have an increased susceptibility to oxidative death by H2O2 exposure, but currently it is unknown if this characteristic is modifiable in vivo. OBJECTIVE: To determine if correction of low vitamin D levels protects lymphocytes from oxidative death and increases Aß1-40 plasma levels in MCI and very early AD (VEAD) patients. METHOD: Sixteen MCI, 11 VEAD and 25 healthy control (HC) voluntaries were evaluated with the Clinical Dementia Rating (CDR), Montreal Cognitive assessment (MoCA), and Memory Index score (MIS). Lymphocyte death was measured by flow cytometry after 20h exposure to H2O2. In patients with low levels of vitamin D -11 MCI, 9 VEAD and 20 HC- lymphocyte H2O2-death, plasma Aß1-40 levels and cognitive status were evaluated pre- and post-vitamin D supplementation for 6 months. RESULTS: Lymphocytes from MCI and VEAD patients showed increased susceptibility to oxidative death at study entry. In MCI, but not VEAD patients, lymphocyte susceptibility to death and Aß1-40 levels plasma levels improved after 6 months of vitamin D supplementation. In addition, cognitive status on follow-up (18 months) improved in MCI patients after vitamin D supplementation. CONCLUSION: Vitamin D supplementation may be beneficial in MCI. The lack of effect in VEAD may be due to a more advanced stage or different characteristics of the neurodegenerative process.
Assuntos
Doença de Alzheimer/tratamento farmacológico , Peptídeos beta-Amiloides/sangue , Colecalciferol/uso terapêutico , Disfunção Cognitiva/tratamento farmacológico , Linfócitos/efeitos dos fármacos , Fármacos Neuroprotetores/uso terapêutico , Fragmentos de Peptídeos/sangue , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/sangue , Biomarcadores/sangue , Morte Celular/efeitos dos fármacos , Morte Celular/fisiologia , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Cognição/efeitos dos fármacos , Disfunção Cognitiva/sangue , Feminino , Seguimentos , Humanos , Peróxido de Hidrogênio/toxicidade , Masculino , Pessoa de Meia-Idade , Nootrópicos/uso terapêutico , Estresse Oxidativo/efeitos dos fármacos , Estresse Oxidativo/fisiologia , Resultado do TratamentoRESUMO
Recent studies suggest that the toxic effects of Aß can be attributed to its capability to insert in membranes and form pore-like structures, which are permeable to cations and molecules such as ATP. Our working hypothesis is that Aß increases extracellular ATP causing activation of P2X receptors and potentiating excitatory synaptic activity. We found that soluble oligomers of ß-amyloid peptide increased cytosolic Ca(2+) 4-fold above control (415 ± 28% of control). Also, ATP leakage (157 ± 10% of control) was independent of extracellular Ca(2+), suggesting that ATP traveled from the cytosol through an Aß pore-mediated efflux and not from exocytotic mechanisms. The subsequent activation of P2XR by ATP can contribute to the cytosolic Ca(2+) increase observed with Aß. Additionally, we found that ß-amyloid oligomers bind preferentially to excitatory neurons inducing an increase in excitatory synaptic current frequency (248.1 ± 32.7%) that was blocked by the use of P2XR antagonists such as PPADS (Aß + PPADS: 110.9 ± 18.35%) or Apyrase plus DPCPX (Aß + inhibitors: 98.97 ± 17.4%). Taken together, we suggest that Aß induces excitotoxicity by binding preferentially to excitatory neuron membranes forming a non-selective pore and by increasing intracellular calcium by itself and through P2XR activation by extracellular ATP leading to an augmention in mEPSC activity. All these effects were blocked with a non-specific P2XR antagonist, indicating that part of the neurotoxicity of Aß is mediated by P2XR activation and facilitation of excitatory neurotransmitter release. These findings suggest that P2XR can be considered as a potential new target for the development of drugs or pharmacological tools to treat Alzheimer's disease. This article is part of the Special Issue entitled 'Synaptopathy--from Biology to Therapy'.